Q&A

Fungal disease on peony can be treated in fall

Q: Two of my peony bushes have developed black and brown patches on their leaves. What is the problem and will it affect next year's growth?

-- Carole Messineo, Long Grove

A: The problem sounds like one of the fungal disease that peonies can get when infectious spores are present on moist spring days. The best way to prevent a new infection next year is by removing and destroying all above-ground portions of the infected plants once they become dormant this fall.

If you want to use a chemical control, spray with a fungicide approved for peonies as soon as new shoots start to emerge next spring. Repeat treatments at the interval recommended on the package label, and continue spraying until flowers begin to open. Timing is important because fungicides can only prevent or limit the spread of a fungal disease; they cannot cure one.

If this problem is recurring, your peonies could be growing in less than ideal conditions, in which case treating with fungicides will provide only a temporary solution. Peonies need full sun, well-drained soil and good air circulation around plants. If needed, wait until early next September to dig, divide and properly replant them.

Q: A 20-year-old clematis that blooms every year appears to be dying. Many of the stems are dry and brown and have only a few green leaves. What should I do?

-- Denise Faris, Chicago

A: It's possible that your plant developed a common problem known as clematis wilt. You should cut the affected stems down to ground level and rake and remove any leaves that have already fallen. Do not add this or any other infected plant material to your compost pile.

The name clematis wilt describes drooping leaves that eventually turn black, but the problem actually occurs near the soil, where a fungus infects weak or damaged stems and causes lesions that kill only the stem above them. The rainy weather in spring and early summer likely contributed to the problem.

Preventive treatment with a fungicide is not recommended for clematis wilt because the problem is rarely fatal. Pruning out diseased stems usually spurs new growth. But because the growing season is almost over, your clematis might wait until spring.